The Echinoderm Fauna of Ascension Island, South Atlantic Ocean

Abstract:

Two recent intertidal collecting expeditions and existing museum collections have added much to knowledge of the Ascension Island echinoderm fauna. Twenty-five species are now known from Ascension; eight are new records. One new species, Holothuria (Halodeima) manningi, and one new subspecies, Echinometra lucunter polypora, are described. Diadema ascensionis Mortensen is regarded as a subspecies of D. antillarum Philippi, and Pseudoboletia atlantica H. L. Clark is regarded as a subspecies of P. maculata Troschel.
The echinoderm fauna of Ascension Island includes 8 amphi-Atlantic species, 3 western Atlantic species, 4 eastern Atlantic species, 5 circumtropical species, 4 species shared only with St. Helena, and I endemic species. There are in addition three endemic subspecies. Twelve species are shared with St. Helena, and both islands are closely similar in terms of numbers and relationships of their faunal components. Colonization of both islands by planktonic larval stages is suggested. Dendrochirotid holothurians, which lack such larval stages, are not represented at either St. Helena or Ascension. The structure of the Ascension fauna seems to have been determined by vagaries of ocean surface and subsurface currents. In contrast, Bermuda, which sits astride the Gulf Stream, has a fauna that is entirely typical of the West Indian region to the the south.